Problem $1$: A power plant emits $120$ pounds of flvash per hour up the stack. The flow rate of the hot gases in the stack is $25$ cubic feet per second. What is the concentration of flyash in $\frac{g}{m^3}($Note: $1kg=2\mathrm{.}2lbm$;$1ft=0\mathrm{.}3048m)?$