A Cepheid variabl star is a star whose brightness alternately increases and decreases. suppose that Cephei Joe is a star for which the interval times of maximum brightness is 5.5 days. its average brightness is 4.8 and the brightness changes by +/-0.065. Using this data, we can construct a mathmatical model for the brightness of Cephei Joe at time t, where t is measured in days:

B(t)= 4.8+0.65sin(2pit/5.5)

(a) find the rate of change of the brightness after t days.

rate of change = ?

(b) find the rate of increase after one day.

rate of increase = ?

please provide steps so I can see how this is worked out. Thank you.