Final answer:
In a qualifying 351 transaction, Lena's gain recognized from contributing land and inventory to a corporation is $40,000, which is treated as a capital gain.
Step-by-step explanation:
In a qualifying 351 transaction, Lena contributes land and inventory to a corporation in exchange for stock and cash. The gain recognized by Lena is calculated by subtracting the basis of the contributed assets from their value. In this case, Lena's gain for the land is $10,000 ($20,000 - $10,000) and for the inventory is $30,000 ($70,000 - $40,000). The total gain recognized by Lena is $40,000. This gain is treated as a capital gain, not as ordinary income or Section 1231 gain.