RMod as closed symmetric monoidal category for a commutative ring

Let $R$ be a commutative ring and $\mathrm{RMod}$ the category RMod Then $\mathrm{RMod}$ admits a closed symmetric monoidal structure via

1. the tensor product for a commutative Ring as tensor functor of a monoidal category
2. the ring $R$ as tensor unit
3. TODO