L2 (I539 Form) Dependent Extension BioMetrics Fees

L2 (I539 Form) Dependent Extension BioMetrics Fees:
There are 3 Dependents for me as i am the L1 Primary applicant (I129/ I797C Form), Dependents are as follows (Spouse/Wife, 1 Daughter & 1 Son) now would like to know for extension do i need to pay Biometrics fees of $85 for only dependents i.e. 3 * 85 = 255 Or 4 * $ 85= $340 including L1 Primary applicant?