DEF Ltd$.$ operates a standard costing system for its products. The following data applies to the last month$$s production of $12,000$ units: Standard data: Materials: $4$ kg per unit at Sh$.8$ per kg Labor: $2\mathrm{.}5$ hours per unit at Sh$.15$ per hour Actual data: Materials used: $46,000$ kg at Sh$.9$ per kg Labor used: $31,500$ hours at Sh$.14$ per hour Required: Calculate the material price variance, material usage variance, labor rate variance, and labor efficiency variance. $(5$ marks$)$