Storage as a rupee cost

Crude for immediate delivery costs ₹7,000/bbl. Storage costs ₹15/bbl per month, paid at the end of each month. The rupee rate is 5.5%. (a) Derive the no-arbitrage upper bound on the three-month futures price, stating the arbitrage strategy if it is violated. (b) Compute it. (c) Show that if storage is instead charged in kind at a proportional rate $u$, the bound is $Se^{(r+u)T}$, and find the $u$ that gives the same three-month bound as (b).