This is a lambda Calculus question

Consider a function if which takes three arguments, a boolean, an expression to evaluate if the boolean is true, and a second expression to evaluate if the boolean is false. Write out the function in lamda calculus.

What is Lamda Calculus:

"Lambda calculus (also written as -calculus or called "the lambda calculus") is a formal system in mathematical logic and computer science for expressing computation by way of variable binding and substitution.