Among the donations with a portion using account credits redemption, how many of them are for projects created by teachers working in a public year-round school?
portion using account credits redemption refers to payment_included_acct_credit = 't'; year-round school refers to school_year_round = 't';
SELECT COUNT(T1.projectid) FROM projects AS T1 INNER JOIN donations AS T2 ON T1.projectid = T2.projectid WHERE T2.payment_included_acct_credit = 't' AND T1.school_year_round = 't'