That would be approximately 339638
Try this:
1) area of f-yard is 60*70=4200 feet²;
2) area of b-yard is 10*30=300 feet², according to condition '<span>on half of his back yard' this area should be 0.5*300=150 feet</span>².
3) total: 4200+150=4350 feet².
It's closer to 4.97 because if you round to the nearest tenths, you will get 4.97.