4 . COMMITMENTS AND CONTINGENCIES The Company is obligated under a noncancelable operating lease for its Longview, Texas office space. The lease was scheduled to expire on April 30, 2018 but the Company executed a lease addendum to extend the term for an additional 36 months resulting in an amended expiration date of April 30, 2021. The lease requires a monthly rental payment by the Company of $2,728. The following is a schedule of future minimum annual rental payments for the next five years required under this operating lease as of March 31, 2018: 2019 $ 32,736 2020 32,736 2021 32,736 2022 2,728 2023  Total $ 100,936 Rental expenses for leased properties were approximately $32,736 and $64,400 during fiscal 2018 and 2017, respectively. The Company leased office space in Humble, Texas for part of fiscal 2017 until the lease expired and was not renewed. At March 31, 2018, the Company had supply agreements in place with certain suppliers that require the Company to purchase minimum quantities of steel on a monthly basis. All such agreements expire on December 31, 2018. The combined minimum monthly purchase requirements under these agreements fall well below the Company's anticipated monthly steel supply needs. Based on the market price of hot-rolled coil at March 31, 2018, the minimum purchase requirements remaining for April 2018 to December 2018 totaled approximately $33,660,000. One of the Companys purchase agreements provides an annual rebate payable to the Company if a certain volume of material is purchased during the term of the agreement. As of March 31, 2018, the Company had not accrued a receivable related to this rebate due to the uncertainty present at that time about whether the Company would purchase the specified volume. The Company will continue to evaluate the likelihood of meeting the purchase requirements related to the annual rebate. If the Company deems receipt of the rebate to be probable, the Company will recognize the rebate on a systematic and rational basis dictated by the underlying tra