Dec 2014 paper task 2 (a)

Hello,
I have badly stuck in understanding how 4.7% is being used for calculating underlying cost of borrowing if interest rates increase by 0.5% to 4.3%.
The similar technique was used for the case comparison if interest rates decrease by 0.5%.
It was used 3.7% for underlying cost of borrowing.

I know it’s a petty matter but seems I can’t move on until I have cleared this point completely.

Thank you,
Daiva