21 million Joules of chemical energy are supplied to a boiler in a power plant. 5,000,000 Joules of energy are lost up the smokestack. The boiler radiates 1.5 million Joules of heat to the atmosphere. What is the efficiency of the boiler?
A) 27.5%
B) 69.0
C) 0.690
D) 6.90%
