1. A service level objective management system, comprising: a service level objective information input unit implemented at least by a hardware including a processor and that inputs, from an administrator of a data center, a service level objective name which is the name of a service level objective defined by the administrator and a condition on which a value defined by the administrator for the service level objective satisfies a requirement value for the service level objective required by a user whom a service is provided from the data center; a group information input unit implemented at least by a hardware including a processor and that inputs a group name which is the name of a service level objective group including at least one service level objective out of service level objectives whose service level objective names are input to the service level objective information input unit by the administrator, a service level objective name of each service level objective included in the service level objective group, a target value defined by the administrator for each of the service level objectives, and a group name of another service level objective group to which the administrator defines a hierarchical relationship with the service level objective group; a user requirement reception unit implemented at least by a hardware including a processor and that receives, from a user terminal of a user who is provided a service from the data center, a service level objective name of a service level objective specified by the user out of service level objectives whose service level objective names are input to the service level objective information input unit and a requirement value required by the user for the service level objective; a combination specification unit implemented at least by a hardware including a processor and that computes, for every combination of service level objective groups from a highest-ranked service level objective group to a lowest-ranked service level objective group among hierarchized service level objective groups, a degree to which the target value of each service level objective in the service level objective group belonging to the combination satisfies the requirement value received from the user terminal with the service level objective name and specifies a plurality of combinations having high degrees by a predetermined criterion; and a combination presentation unit implemented at least by a hardware including a processor and that transmits display contents of a screen displaying the individual combination of service level objective groups specified by the combination specification means unit to the user terminal and receives information on the combination of service level objective groups selected by the user from the user terminal.