what is the boiling point of the feed?

Problem Statement: The feed to a depropaniser column operating at $15$atm contains $6\%$ ethane, $41\%$ propane, $28\%$ i$-$butane, $23\%$ n$-$butane, $23\%n-$butane and $2\%n-$pentane. The distillate which leaves the partial condenser as vapour has $98\%$ of the propane from the feed whereas $98\%$ of the of the ibutane is recovered in the saturated liquid bottoms product. The partial condenser may be assumed to operate at equilibrium and the reflux ratio is $1\mathrm{.}5R_{\text{m}\text{i}\text{n}}.$ The bottoms product exits the reboiler as a saturated liquid. You may assume negligible pressure drop throughout the tower.

Note: You will need to find your own equilibrium and enthalpy data. Remember to include the reference. Use a constant relative volatility across the tower for each component. Determine the value of the relative volatility at the average tower temperature i$.$e$.$ the average of the temperatures in the condenser and reboiler.