Jack and Jill are not married and own farm land titled as Joint Tenants with Rights of Survivorship. Jack originally contributed $90,000 and Jill contributed $60,000 towards the purchase price. The land is currently valued at $800,000 and each of them has a 50% interest in the property. If Jack died today, what amount of the value of the farm land would be included in his gross estate?

a. $90,000"

"b. $400,000"

"c. $480,000"

"d. $800,000"