(a) With respect to any prescription drug for which a rebate amount has been negotiated pursuant to Section 130403, upon presentation of a program registration card issued pursuant to Section 130401, a participating pharmacy shall charge Medicare beneficiaries a price for a prescription drug that does not exceed the following computed price:

1. (1) The Medi-Cal reimbursement rate for the prescription drug, and an amount, as set by the department, to cover electronic transmission charges.
2. (2) The amount ascertained pursuant to paragraph (1) shall be reduced by the rebate amount negotiated by the department pursuant to Section 130403.