case study : A factory, working for $50$ hours a week, employs $100$ workers on a job work. The standard rate is $`1$

an hour and standard output is $200$ units per gang hour. During a week in June, ten employees were

paid at $80$ p$.$ an hour and five at $`1\mathrm{.}20$ an hour. Rest of the employees were paid at the standard rate. Actual number of units produced was $10,200$ Calculate labour cost variances