Acepheid variable star is a star whose brightness alternately increases and decreases. for a certain star, the interval between times of maximum brightness is 5.7 days. the average brightness of this star is 2.0 and its brightness changes by ±0.45. in view of these data, the brightness of the star at time t, where t is measured in days, has been modeled by the function b(t)=5.0+0.45 sin (2πt/4.6), where t is measured in days. find, correct to two decimal places, the rate of increase after five days.