For the 3% extra, it depends on the average daily balance up to a cap of 50K.
Therefore, the bonus interest is calculated as:
$50,000 * 3% / 12 = $125
For the base interest of 0.05%, interest is accrued on a daily basis.
Therefore, from 1/5 to 9/5, the base interest for one day is calculated as:
$30,000 * 0.05%/365 = $0.041096.
Do the following for the following 8 days...
($30,000+$0.041096) * 0.05%/365....
At the end of 9 days, the total interest earned for the 9 days should be = $0.36987
From 10/5 to 31/5, the base interest for one day is calculated as:
$60,000.36987 * 0.05%/365 = $0.082192
Do the following for the following 21 days...
($60,000.36987 + $0.082192) * 0.05%/365...
At the end of 22 days, the total interest earned for the 22 days should be = $1.808256.
Total interest earned = $2.178121