Jan and Dean each contribute $$1,000$ to buy Whitacre. They take title as joint tenants. Jan dies when the property is worth $$500,000.$ How much of it will be included in Jan's estate?

a$)$ All $$500,000.$

b$)$ None of it$.$ Because it is a joint tenancy all of the property goes to Dean at Jan's death. $($Incorrect answer$)$

c$)$ $$1,000$

d$)$ $$250,000$