def calculate(a, b):
    """Return a dict with the four basic operations on (a, b).

    Convert both inputs with float() so output is consistent.

    Returned dict has these exact keys:
      "sum"        — a + b
      "difference" — a - b
      "product"    — a * b
      "quotient"   — a / b

    calculate(10, 5) -> {"sum": 15.0, "difference": 5.0,
                        "product": 50.0, "quotient": 2.0}
    """
    pass