Question

If a bar dot 7a bar - 5b bar = 0 and a bar - 4b bar dot 7a bar - 2b bar = 0, then what is the value of a bar and b bar?
1) a bar = 0, b bar = 0
2) a bar = 5, b bar = 7
3) a bar = 4, b bar = 2
4) a bar = 7, b bar = 5