Answer
Exhaust is ejected at a rate of $~~27~kg/s$
Work Step by Step
In part (a), we found that the thrust of the engine is $~~8.0\times 10^4~N$
We can find $R$, the fuel consumption rate:
$R~v_{rel} = F_{thrust}$
$R = \frac{F_{thrust}}{v_{rel}}$
$R = \frac{8.0\times 10^4~N}{3.0\times 10^3~m/s}$
$R = 27~kg/s$
Exhaust is ejected at a rate of $~~27~kg/s$
