Would anyone happen to know how I can calculate an average off of HHI ranges and/or age ranges and include in a Dashboard Widget?

For example, if I have the following HHI ranges: 

• 2% Under $25,000
• 6% $25,000 - $49,999
• 24% $50,000 - $99,999
• 22% $100,000 - $149,999
• 12% $150,000 - $199,999
• 19% $200k+

If I were to calculate this manually, I would have to assume a mid-point first:

• Under $25,000 (Assumed Midpoint: $12,500), 2%
• $25,000 - $49,999 (Assumed Midpoint: $37,500), 6%
• $50,000 - $99,999 (Assumed Midpoint: $75,000), 24%
• $100,000 - $149,999 (Assumed Midpoint: $125,000), 22%
• $150,000 - $199,999 (Assumed Midpoint: $175,000), 12%
• $200,000 and above (Assumed Midpoint: $250,000), 19%

Calculation nmidpoint * (percentage/100)] = $116,500

But, how can this be done in Qualtrics and is this the correct way to go about calculating this? Open to any suggestions - thank you!