Based on the record, the trial court must assess the violations of the sanitary code and determine the percentage by which the tenant’s use and enjoyment of the premises has been diminished by the existence of those violations. McKenna v. Begin, supra at 311. The court is given broad discretion to determine whether minor violations affected the rental value of premises, thus breaching the warranty of habitability and entitling the tenant to damages. Boston Housing Authority v. Hemingway, supra at 200-01, n.16; McKenna v. Begin, supra at 307-08. A tenant need not introduce expert testimony as to the value of particular violations of the sanitary code. Id. at 311. Damages for a breach of the implied warranty of habitability may not be determined by speculation or guess, although an approximate result is permissible if the evidence shows the extent of the damages to be a matter of just and reasonable inference. Id. The tenant must therefore make some showing, through her own testimony or otherwise, of the extent to which the violations interfered with or adversely impacted the use and enjoyment of the premises. Poncz v. Loftin, 34 Mass.App.Ct. 909, 911 & n.2, rev. den., 415 Mass. 1102 (1993). See also Brown v. LeClair, 20 Mass.App.Ct. 976, 977-78 (1985) (upholding a damage award for breach of the warranty of habitability where the tenant introduced photographs of the premises and testified as to the personal property lost and personal injury suffered as a result of the violations).