Which formula below correctly states Coulomb's Law? A. F = kqq/r2
B. F = kqq/r
C. F = qq/kr2
D. F = kr2/qq

F is directly proportional to the product of the charges

F is inversely proportional to the square of the distance between them

from above 2 equation:-

we get:-

To remove proportionality sign we use constant for this case we r using constant k

So your answer is :-

this means that the temperature of both substances will be equal

b.a device that inputs heat into a cool object