def METHOD_NAME(blk, A, B):
    """
    Generate expression for capital cost of UV reactor.
    """
    t0 = blk.flowsheet().time.first()
    Q = pyo.units.convert(
        blk.unit_model.properties_in[t0].flow_vol,
        to_units=pyo.units.m**3 / pyo.units.hr,
    )
    E = pyo.units.convert(blk.unit_model.electricity[t0], to_units=pyo.units.kW)
    expr = pyo.units.convert(
        A * Q + B * E,
        to_units=blk.config.flowsheet_costing_block.base_currency,
    )
    return expr