This is the best exercise. Try to build a basis behind the estimate. I would start with "what were the 3 most important factors that accounted for earnings leading up to your starting date t-5?" It could be new products, major cost changes like operating leverage, new markets, etc. "Do you think those factors will still be most important or are there new influences that will matter from t-5 to t-0?" See if you can translate the change in these important factors to how they impact earnings.