guarantees and warranties in april 2015 , we entered into joint venture arrangements in saudi arabia . an equity bridge loan has been provided to the joint venture until 2020 to fund equity commitments , and we guaranteed the repayment of our 25% ( 25 % ) share of this loan . our venture partner guaranteed repayment of their share . our maximum exposure under the guarantee is approximately $ 100 . as of 30 september 2015 , we recorded a noncurrent liability of $ 67.5 for our obligation to make future equity contributions based on the equity bridge loan . air products has also entered into a sale of equipment contract with the joint venture to engineer , procure , and construct the industrial gas facilities that will supply gases to saudi aramco . we will provide bank guarantees to the joint venture of up to $ 326 to support our performance under the contract . we are party to an equity support agreement and operations guarantee related to an air separation facility constructed in trinidad for a venture in which we own 50% ( 50 % ) . at 30 september 2015 , maximum potential payments under joint and several guarantees were $ 30.0 . exposures under the guarantee decline over time and will be completely extinguished by 2024 . during the first quarter of 2014 , we sold the remaining portion of our homecare business and entered into an operations guarantee related to obligations under certain homecare contracts assigned in connection with the transaction . our maximum potential payment under the guarantee is a320 million ( approximately $ 30 at 30 september 2015 ) , and our exposure will be extinguished by 2020 . to date , no equity contributions or payments have been made since the inception of these guarantees . the fair value of the above guarantees is not material . we , in the normal course of business operations , have issued product warranties related to equipment sales . also , contracts often contain standard terms and conditions which typically include a warranty and indemnification to the buyer that the goods and services purchased do not infringe on third-party intellectual property rights . the provision for estimated future costs relating to warranties is not material to the consolidated financial statements . we do not expect that any sum we may have to pay in connection with guarantees and warranties will have a material adverse effect on our consolidated financial condition , liquidity , or results of operations . unconditional purchase obligations we are obligated to make future payments under unconditional purchase obligations as summarized below: .
what was the decrease observed in the unconditional purchase obligations during 2016 and 2017?
approximately $ 390 of our long-term unconditional purchase obligations relate to feedstock supply for numerous hyco ( hydrogen , carbon monoxide , and syngas ) facilities . the price of feedstock supply is principally related to the price of natural gas . however , long-term take-or-pay sales contracts to hyco customers are generally matched to the term of the feedstock supply obligations and provide recovery of price increases in the feedstock supply . due to the matching of most long-term feedstock supply obligations to customer sales contracts , we do not believe these purchase obligations would have a material effect on our financial condition or results of operations . the unconditional purchase obligations also include other product supply and purchase commitments and electric power and natural gas supply purchase obligations , which are primarily pass-through contracts with our customers . purchase commitments to spend approximately $ 540 for additional plant and equipment are included in the unconditional purchase obligations in 2016. .