Copy of

The average time per unit for constructing $30$ electrical assemblies is $170$ hours. The rate of learning for doubled averages is about $0\mathrm{.}90.$ The time to build the $50$th unit is $($rounded integer value in hours$)$:

A$.$

$152$

B$.$

$116$

C$.$

$134$

D$.$

$98$