Assuming 100PSA, CPR = 6% * $\frac{10}{30}$ = 2%
Thus, 175PSA = 1.75 × 2% = 3.50%

SMM = $1 - (1 - 0.035)^{1/12} = 0.002965$

Note that, a pool of mortgages is said to have 100%- PSA if its CPR starts at 0 and with monthly increments of 0.2 % until 6% is reached in month 30, after which the CPR remains constant at 6%. In other cases, the prepayment scenarios are specified as multiples of 100% PSA.

Note that, PSA = $\left[\frac{\text{CPR}}{0.2(m)}\right] * 100$

where,
m = number of months since origination.