Can I play Black Ops 7 using Dell Optiplex?

Minimum specifications needed to play the Call of Duty: Black Ops 7 Beta:

• OS: Windows 10 64 Bit (latest update)*
• CPU: AMD Ryzen™ 5 1400 or Intel® Core™ i5-6600
• RAM: 8 GB
• Video Card: AMD Radeon™ RX 470 or NVIDIA GeForce® GTX 970 / 1060 or Intel Arc A580
• Video Memory: 3 GB
• Storage Space: SSD with 60 GB available space

 this means Optiplex 7040 MT with psu upgrade can meet minimal requirement.

Recommended specs to run at 60 FPS in most situations with all options set to high:

• OS: Windows 10 64 Bit (latest update)* or Windows 11 64 Bit (latest update)*
• CPU: AMD Ryzen 5 1600X or Intel Core i7-6700K
• RAM: 12 GB
• Video Card: AMD Radeon RX 6600XT or NVIDIA GeForce RTX 3060 or Intel Arc B580
• Video Memory: 8 GB
• Storage Space: SSD with 60 GB available space

it is possible to upgrade 7040 MT cpu to 6700k and Dell premium tower air cooler and psu to support RTX3060 to meet recommended requirement.

https://support.activision.com/black-ops-7/articles/pc-system-requirements-for-black-ops-7