The normal monthly temperatures (°F) for Omaha, Nebraska, are recorded below.

Month

Jan Feb Mar

Apr May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

1

2

3

4

5

6

7

8

9

10

11

12

Temp.

21°

27°

390520620

720

770

740

650

53°

39°

25°

a. Write a sinusoidal function that models Omaha's monthly temperature variation

b. Use the model to estimate the normal temperature during the month of April.