Berkson Inc.$\text{'}$s costs at $150,000$ units of production are $$240,000($the high point of production$)$ and $$152,500$ at $80,000$ units of production $($the low point of roduction$),$ the variable cost per unit using the high$-$low method of cost estimation is:

$$1\mathrm{.}60$

zero

$$1\mathrm{.}91$

$$1\mathrm{.}25$