To solve for the consumer surplus, the formula is;
Consumer surplus = total value – actual value
If jena is willing to pay for $75 then = $75 – $65 = $10
If Jane on the other hand is willing to pay for $85 then = $85 - $65 = $20
To combine the amount of Jena and Jane to be able to get both of their consumer surplus,
= $10 + $20 = $30
The combined amount of consumer surplus of Jena and Jane is $30.