If the player has more than 5000 DP then the following applies:
\operatorname{earnMultiplier}(bank)= 5000 / (bank * 10)
earnMultiplier(bank)=5000/(bank∗10) \operatorname{earnMultiplier}(bank)= 5000 / (bank * 10)
That means if you have 10,000 DP then:
5,000 / (100,000) \ = 0.05 \ = \text{5% multiplier}
5,000/(100,000)=0.05=5% multiplier