Help! Coupon Train question

On a really great train that has 2 B2G1 coupons I want. I don't have any "b2g1" coupons, just b1g1 and not something that I would consider the same value.

They're the Lipton b2g1, and I usually pay $4.99 max for the drinks, so I'd value these at $5.00 bonus for me? Should I put in say the b1g1 and an extra $10.00 of coupons? The conductor is not on and I want to send this on as soon as possible.

ask the train conductor or the rider they are going to

Neither are available and I will be mailing this first thing tomorrow AM.

So, I gave 3 b1g1's and a couple extra coupons to make up what I feel the value is worth :)