Two long, parallel wires, fixed in space, carry currents I1 and I2. The force of attraction has magnitude F. What currents will give an attractive force of magnitude 4F?

a) 2I₁ and ½I₂
b) I₁ and ¼I₂
c) ½I₁ and ½I₂
d) 2I₁ and 2I₂
e) 4I₁ and 4I₂