'W' is a message parameter in a ECC based protocol. I could not understand one thing the number of scalar multiplications in this w. My paper says, it is one.

W=bh(h(PW||a)||username)Ppub
where 'b' and 'a' is a random integer, PW password, Ppub a public key.

Can anybody tell me, that Once hash value is computed
1.does b get multiplied with the hash value, and then scalar multiplication is performed with Ppub, or
2. does hash get scalar multiplied with Ppub. and then the resulting point multiplied with b, in this case there might be two scalar multiplications. or
3. first b is multiplied with Ppub, then again the resulting point multiply with hash value.

For scalar multiplication with Ppub, we must have some scalar number. Do we get it from hash function. Can we also get some other number than integer out of hash.
regards,
Azeem