1) Place the answer in proper amount of significant digits and unit:

K = [6.63x10^(-34) J.s] (7.09x10^14 s) - [2.17 x 10^(-19) J]

Note: J.s = Joule x sceonds

Can someone help me with this question, please? I don't know how to write the answer with the proper amount of significant digits and unit.....

I got:

K=4.70x10^(-19) J.s^2 - 2.17x10^(-19) J

Note: J.s^2 = Joule x seconds^2

They have different units, how can I subtract this and what are the final units? What would be the correct number of significant digits in the final answer?