This Work Letter shall set forth the obligations of Landlord and Tenant with respect to the improvements to be performed in the Premises for Tenant’s use.  For the purposes of this Lease, “ Landlord’s Fourth Amendment Work ” consists of the Base Building Work and the Tenant Improvement Work, each as hereinafter defined.  The “ Base Building Work ” is identified on the Landlord/Tenant Responsibility Matrix attached hereto as Exhibit B-1, Fourth Amendment .  The “ Tenant Improvement Work ” is: (i) identified on the Landlord/Tenant Responsibility Matrix attached hereto as Exhibit B-1, Fourth Amendment ,  (ii) shown on the Space Plans attached hereto as Exhibit B-2, Fourth Amendment, Sheet 1 , and (iii) shown on the Tenant Equipment List for the First Floor attached hereto as Exhibit B-2, Fourth Amendment, Sheet 2 .   The Base Building Work shall be performed at Landlord’s sole cost and expense.  The Tenant Improvement Work shall be performed at Tenant’s cost and expense, subject to Landlord’s Fourth Amendment Contribution, as hereinafter set forth.