A level physics- Engineering option question (2)

can someone help me with this question so :
A four-stroke diesel engine with four cylinders is running at constant speed on a test
bed. An indicator diagram for one cylinder is shown in the figure below and other test
data are given below:
measured output power of engine (brake power) = 55.0 kW
fuel used in 100 seconds = 0.376 litre
calorific value of fuel = 38.6 MJ litre–1
engine speed = 4100 rev min–1

calculate the indicated power?
-so the area of the P-V loop was 470
-so I calculated the indicated engine power to be = 470 x 4 x (4100/60)
-but the markscheme says the indicated power= 470 x 4 x (4100/60) x 0.5
where is the 0.5 from ?

Original post by 1234kelly

can someone help me with this question so :
A four-stroke diesel engine with four cylinders is running at constant speed on a test
bed. An indicator diagram for one cylinder is shown in the figure below and other test
data are given below:
measured output power of engine (brake power) = 55.0 kW
fuel used in 100 seconds = 0.376 litre
calorific value of fuel = 38.6 MJ litre–1
engine speed = 4100 rev min–1

calculate the indicated power?
-so the area of the P-V loop was 470
-so I calculated the indicated engine power to be = 470 x 4 x (4100/60)
-but the markscheme says the indicated power= 470 x 4 x (4100/60) x 0.5
where is the 0.5 from ?