Help with complex formula, with XLOOKUP

I'm hoping that somebody smarter than me can help me out with a complicated formula I'm having trouble designing. Attached is the file.

Cell R16 should calculate the total kg of a medicine called "F100" based on the number of days in treatment (user entered data in R13), the average daily weight gain (user entered data in R14), and weight of the patient at admission (user entered data in R4). The weight-based dosage chart of F100 is in columns B-G.


The formula should look something like this:
On day 1 of treatment, the patient should get the amount listed in the dosage chart (Column G based on their weight that day) +
On day 2 of treatment, the patient should get the amount listed in the dosage chart (Column G based on their weight that day, which is weight at admission plus the weight gained since admission) +
.....
On day N of treatment (cell R13), the patient should get the amount listed in the dosage chart (Column G based on their weight that day, which is weight at admission plus the weight gained since admission)
= The total amount provided to the patient based on their weight at admission and average daily weight gain

Many thanks for any suggestions!