The rate of temperature rise is 2 degrees/minute.
The relation between temperature and time is of the form
y = 2x + b
where
x = time, minutes,
y = temperature, Celsius
When x = -4 min, y = - 4°C because the temperature was - 4°C 4 minutes ago. Currently, x = 0.
Therefore
-4 = 2(-4) + b
-4 = - 8 + b
4 = b
Part A
The relation is y = 2x + 4
Part B
When x = 15 (15 minutes from now), the temperature will be
y = 2(15) + 4 = 34°C
Answer: 34°C