$3\mathrm{.}2$ Assuming unit formation width, determine the average porosity for the fol$-$ lowing system when $0=0\mathrm{.}20,0=0\mathrm{.}11,0=0\mathrm{.}29,$ L $=0\mathrm{.}35$L$,$ and h$,=$ h $=0\mathrm{.}5$ h$.$