Sheridan Service sells oil at a markup of $42\%$ of the selling price. Sheridan paid $$0\mathrm{.}91$ per litre of oil.

$($a$)$ What is the selling price per litre?

$($b$)$ What is the rate of markup based on cost$?$

$($a$)$ The selling price per litre is $

$($Round the final answer to the nearest cent as needed. Round all intermediate values to six decimal places as needed.$)$