plz help me with this question in step by step, and plz write the answers with four decimal places, thx.

[3+3=6 points ] The revenue of a of a summer resort is approximately R(t)=3(7+cos26(t+3)2sin6(t+3)),0t12 thousand of dollars during the tth week ( t=1 corresponds to the first week of June) (a) Find the week in which the revenue is increasing most rapidly. (b) When does the resort realized the greatest revenue