How to calculate variance from EWMV model

[npdrbong]

In the original article, subjective utility is calculated from the linear combination of mean and variance of expected value.
To do this, we can calculate mean and variance of:

than, I can't derivate p (1 - p ) {r + lambda(l-1)r}^2.. Does anyone know how to derivate this? or I missed with calculate variance of expected value?