$(30)$ A footing ${2\mathrm{.}5}^{**}2\mathrm{.}5m$ is located at a depth of $2,0m$ in a sand, the internal friction angle is $38.$

For ${}^{?}==38,N_{}=67,Nq=49,$ Saturated unit weight is $20k\frac{N}{m^3},$ unit weight of water is $10k\frac{N}{m^3},$ Natural unit weight is $18k\frac{N}{m^3},$ qutr $-DNq+0\mathrm{.}4B{N}_{}.$

a$)$ Determine the allowable bearing capacity. If there is no ground water.

b$)$ Determine the allowable bearing capacity. If the ground water table is $2,0m$ depth