Answer: tip would increase by $2.44
Step-by-step explanation:By applying Richard's method: tip given= 20% of 48.8
Tip given=$9.76
Now applying Davina's method: cost need to be paid after taking coupon into an account= 48-25%48.8= $36.6
Tip given =20% of 36.6=$7.32
Amount of tip given increased= $9.76-$7.32=$2.44