The given function is

with
t = time, hours
f = temperature, °C
Because the maximum and minimum values for the Sine function are +1 and -1 respectively,
The maximum value of f = 33 - 20 = 13.
The minimum value of f = -33 - 20 = -53.
The period, T, is given by

Answer:
Maximum: 13°; Minimum: -53°; period: 4 hours