RHP wattage recommendation?

[HanabiraAsashi]

Hello,
My room temp is about 70 degrees, my tank is 36x18x18. What reptile basics RHP should I get? Im hoping i can have my snake cozy with a 40 watt but im thinking im going to need the 80.

Thanks!

Edit: I should add that the RHP and the UTH will be the only heat sources. Bulbs are LED