When a 4 g peanut is burned, it warms 300 ml of water 45 °c. what was the energy content of the peanut?

Answer is: 13500 cal.
m(water) = V(water)·d(water) = 300ml·1g/ml = 300g.
ΔT = 45°C, temperature change.
Calorie is amount of energy (heat) needed to increase the temperature of one gram of water by 1°C.
To raise the temperature of 300 grams of water for 45°C:
Heat in calories = mass in gram x temperature change °C  x specific heat (cal / gram·°C). Q = m·ΔT·c.
Q = 300g · 45°C · 1cal/g·°C = 13500 cal.

The answer is celsius 

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.