For a mixture of $10$ mol$-\%$ methane, $20$ mol$-\%$ ethane, and $70$ mol$-\%$

propane at $50(\backslash$deg F$)$ determine:

$($a$)$ The dewpoint pressure

$($b$)$ The bubblepoint pressure

The K$-$values are given by Fig$\mathrm{.}10\mathrm{.}13$