MA process

[chmakar]

Assume returns r are generated by the following model:

rt= m+et+a et-1 + b et-2 (m, b and a are constants) and e are IID

How could i use this model for forecasting? Suppose I am at time t=T. How can I (and assuming I know all its
parameters), predict the return at time t=T+2?

regards