Syarikat Dominic Lao uses the high$-$low method to estimate the cost function. The information for $2021$ is provided below:

Costs Machine$-$hours Labour

Highest observation of cost driver $400$ RM$20,000$

Lowest observation of cost driver $240$ RM$13,600$

What is the slope coefficient per machine$-$hour?

Question $20$ options:

A$)$ RM$56\mathrm{.}66$

B$)$ RM$0\mathrm{.}10$

C$)$ RM$40\mathrm{.}00$

D$)$ RM$50\mathrm{.}00$