I need help with this question

Question

When a magnetic south pole with a strength of 25 units is placed 5.0 cm from another magnetic pole, it experiences a repulsion of 450 dynes. What is the strength of the second pole?

If you can, you could just show me the formula and where to put the variables in the formula and explain to me how to solve it, Thank you!

Answer 1

F=450 H=25 r=5

F=(m₁m₂)/(µr²) in vacuum µ=1, F=(m₁m₂)/(r²); H=B=m/r² and m=Br²; then F=(H₁H₂ r²) and

H₂=F/ (H₁r²)=450/(25*5²)=0.72 units