CORRECT AND DETAILED ANSWER NEEDED! THANK YOU!

Sandra inherited $200,000 from her grandmothers estate and decided to invest the money. Sandra and her husband, Dan, purchased a parcel of land in an undeveloped, wooded area a few blocks from their current home. At the time of purchase, they felt that in the future they may use the land to build a new home. However, they were equally motivated by the fact that the land was a solid investment and would very likely gain value quickly. They ended up selling the land four years after the purchase for $350,000.

Should the $150,000 gain be treated as a capital gain or as business income? Justify your conclusion.