= Solution
The 21.1 cm line is neutral <hydrogen>'s hyperfine spin-flip transition, observed with <Radio telescope>[radio telescopes] and interferometers in the cool/warm neutral gas disk, often beyond the bright stellar disk. The mean wavelength gives $z=22.0/21.1-1\simeq0.0427$ and, using the stated low-redshift Hubble approximation, $d\simeq180$ Mpc. A 16-arcsecond angular <radius> gives $R\simeq14$ kpc. For a thin circular disk, $\cos i=8/32$, so $i\simeq75.5^\circ$ from face-on.
The original <Frequency spectrum>[spectrum] reaches roughly 21.98 and 22.02 cm: $v_{\mathrm{los,max}}\simeq c(0.02/22.0)\simeq273$ km s$^{-1}$. Deprojecting gives $\boxed{v_{\max}\simeq282\ \mathrm{km\,s^{-1}}}$. A spherical dynamical estimate $M(<R)\simeq v^2R/G$ gives $\boxed{M\sim2.6\times10^{11}M_\odot}$. A thin massive disk is not spherical: its exact rotation-to-total-mass coefficient depends on radial <mass> profile. The no-exterior-matter assumption does not uniquely fix that coefficient, so the quoted result is the conventional order-of-magnitude dynamical estimate. Cosmological <luminosity> and angular-diameter distances differ at this redshift; the source's simple Hubble-distance convention is being used consistently.
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