Crude oil with a flow rate of $1000$ kg$/$hour flows through a double$-$pipe heat exchanger and is heated from $30\backslash$deg C to $90\backslash$deg C$.$ Heat is initially supplied from kerosene, which is at $230\backslash$deg C and flows through a space between two pipes $($annular space$).$ When the minimum temperature difference $($approach temperature$)$ between the fluids is $12\backslash$deg C$,$ calculate the required heat transfer area and the flow rate of kerosene: a$)$ when the fluids flow in countercurrent and b$)$ in parallel flow. Data: Overall heat transfer coefficient, U$=450$ W$/$m$2.$K; Specific heat of crude oil Cp$=0\mathrm{.}56$ kcal$/$kg$.\backslash$deg C; Specific heat of kerosene, Cp $=0\mathrm{.}60$ kcal$/$kg$.$ is $\backslash$deg C$.$