Probability

The probability distribution of a random variable X is given below :

table {width: 100%;border-collapse: collapse;margin: 20px 0;}th {background-color: blue;color: white;border: 1px solid lightgrey;padding: 10px;}td {border: 1px solid lightgrey;padding: 10px;text-align: left;}

X	4k	$\frac{30}{7}k$	$\frac{32}{7}k$	$\frac{34}{7}k$	$\frac{36}{7}k$	$\frac{38}{7}k$	$\frac{40}{7}k$	6k
P(X)	$\frac{2}{15}$	$\frac{1}{15}$	$\frac{2}{15}$	$\frac{1}{5}$	$\frac{1}{15}$	$\frac{2}{15}$	$\frac{1}{5}$	$\frac{1}{15}$

If E(X) = $\frac{263}{15}$, then P(X < 20) is equal to :