**Let the two forces be x and y**

**Greatest resultant ( parallel cosz=1) = x+y = 7N ------------(1)**

**Least Resultant ( antiparallel cosz= -1) = x-y = 3N -------------(2)**

**Solving equation (1) and (2) we get x =5N, y =2N**

**Each force is increased by 3N**

**Therefore x = 8N, y = 5N**

**Resultant vector = ( x**^{2} + y^{2} +2xycos60^{o})^{1/2}

**= (64 + 25 + 2*8*5*1/2)**^{1/2}

**= √129**