To get the answer, you must know first the formula for heat.
Heat = mass X specific heat X change in temp
We know that the mass is 600
Specific heat is 1
And the change in temperature is 70 – 25 which is 45.
Now plugging in those values:
Heat = 600 x 1 x 45 = 27,000 calories
Note: calorie is a unit of heat