Assume that Decedent's mother predeceases her and in addition to the brokerage account valued at $200,000 owned as a tenancy-in-common with her daughter, and the $1 million life insurance policy owned on her daughter which has a replacement value of $300,000, mother has a life estate in a piece of real estate which is valued at $700,000. What is the value of mother's gross estate?

A. $ 100,000 B. $ 200,000 C. $ 400,000 D. $1,900,000