To have an average speed of 70 mph over 5 hours he needs to travel 70*5=<<70*5=350>>350 miles.
He drove 60*3=<<60*3=180>>180 miles in the first 3 hours
He needs to travel another 350-180=<<350-180=170>>170 miles over the next 2 hours.
His speed needs to be 170/2=<<170/2=85>>85 mph
#### 85